Dendritic cells (DCs) in skin and other tissues play major roles in the presentation of antigen to T cells. Chemokines are small molecules produced by a variety of cells and induce migration in cells expressing appropriatereceptors. We wish to understand the role chemokines and chemokine receptors inbiology of DC trafficking and function. Most of our studies are conducted with bona fide DCs derived after culturing mouse skin for several days. DCs spontaneously migrate from skin and into media where they can be collected. Weperform a variety of assays including: chemotaxis assays, RT-PCR gene expression analysis, and fluorescence microscopy. We have found that CC chemokine receptor 7 (CCR7) is strongly upregulated in skin DC following exposure to inflammatory cytokines. Secondary lymphoid-tissuechemokine (SLC), a ligand of CCR7, was found to be constitutively expressed by dermal lymphatic endothelium and was highly potent in stimulating mature DC migration in vitro. Using antibodies directed against SLC, we found that DCtrafficking from peripheral tissue to regional lymph nodes could be significantly inhibited in a murine model of DC trafficking, thus providingevidence the SLC and CCR7 play a functional role in the trafficking of DC to secondary lymphoid organs. Upon further investigation, we have found that other chemokines may play a role in this trafficking process. Using a lymphangioma model which mimicks chemokine expression by lymphatic endothelium, we have observed the expression of multiple chemokines including SDF-1 and SLC. Interestingly, the system treatment of mice with a small peptide inhibitor of SDF-1s receptor(CXCR4)led to the reduction of migration of skin DC from peripheral tissue to regional lymph nodes.We have also found that maturing DCs produce a variety of chemokines including fractalkine, the lone member of the CX3C family of chemokine. Expression of fractalkine was enhanced by ligation of CD40 on DC, suggesting a mechanism bywhich CD40 ligation primes DC to become better antigen presenting cells. Although initially expressed in a surface bound form, fractalkine can be cleaved from the cell surface, and the cleaved form induces migration of IL-2 stimulatedT cells. Because of the unique surface bound stucture of fractalkine on the DC, it is possible that fractalkine acts as a cell surface adhesion molecule in addition to possibly acting as a T cell chemoattractant for the DC. Fractalkine may also serve to attract mast cells to epidermal or dermal dendritic cells. Our recent work has shown that mast cells (including dermal mast cells isolated from neonatal foreskin dermis) express the fractalkine receptor (CX3CR1) and respond well to fractalkine in chemotaxis assays in vitro. Fractalkines constitutive expression by endothelial cells and also nerves may be a mechanism to recruit MC to these cells in vivo under non-inflammatory conditions. - antigen presentation, chemokines, inflammation, inflammatory skin disease, adhesion molecules, - Human Subjects & Human Tissues, Fluids, Cells, etc.